The present invention relates to the constitution of a heat exchanger for an air-conditioning apparatus.
FIG. 10 illustrates the constitution of a heat exchanger disclosed in Japanese Patent Application No. 59-264087. This heat exchanger comprises corrugated fins 1 arranged in layers and each having a plurality of through holes 13 and trapezoidal corrugations, and pipes 2 disposed so as to disturb fluid flows which flow in a direction indicated by an arrow Z through fluid passages formed between the layers of the corrugated fins 1. In the heat exchanger shown in FIG. 10, the corrugated fins 1 are arranged so that the ridges and the furrows of one of the adjacent corrugated fins 1 are disposed opposite the furrows and the ridges of the other, respectively.
FIG. 8 is a sectional view of assistance in explaining the function of the heat exchanger of FIG. 10. Referring to FIG. 8, suppose that a first fluid passage 51 and a second fluid passage 52 are formed between the fins 1a and 1b and between the fins 1b and 1c, and that the flow rate and the total pressure of the primary fluid, such as air, that flows through the first fluid passage 51 are the same as those of the primary fluid that flows through the second fluid passage 52. Then, in a plane corresponding to line X--X perpendicular to the direction of the fluid flow indicated by an arrow Z, the first fluid passage 51 and the second fluid passage 52 are different from each other in sectional area, more specifically, the sectional area of the first fluid passage 51 is greater than that of the second fluid passage 52. Accordingly, the velocity of the primary fluid across the cross section of the first fluid passage 51 corresponding to line X--X is smaller than that across the cross section of the second fluid passage 52 corresponding to line X--X, and hence the static pressure of the primary fluid in the first fluid passage 51 in the vicinity of the cross section is higher than that of the primary fluid in the second fluid passage 52 in the vicinity of the corresponding cross section. Consequently, part of the primary fluid flowing through the first fluid passage 51 flows through the through holes 13 into the second fluid passage 52. With particular reference to the fin 1b, part of the primary fluid flows alternately from the primary fluid passage 51 into the second fluid passage 52, and from the second fluid passage 52 into the first fluid passage 51, through the through holes 13 formed in the fin 1b, according to the arrangement to the corrugations of the fin 1b. This arrangement of the corrugated fins 1 forms fluid passages each having a sequential arrangement of planes for uniform suction and those for uniform blowing, which are arranged along the direction of the flow of the primary fluid. In the section for uniform suction, since the thickness of boundary layers formed over the heat transmitting surfaces is very small, the heat transmission promoting effect is enhanced remarkably, while in the section for uniform blowing, the same high heat transmission promoting effect is provided by the effect of the repetition of accelerating sections. Furthermore, in the stagnation region behind the pipe 2, the primary fluid is able to flow from one to the other fluid passage through the through holes 13 without stagnating in the stagnation region, and thereby the heat transmitting characteristics of the portion in the vicinity of the stagnation region of the heat exchanger is improved. Thus, the inventor of the heat exchanger disclosed in Japanese Patent Application No. 59-264087 states that the invention provides a heat exchanger capable of very high heat transmitting performance which has never been expected.
The inventor states also that the heat exchanger of his invention is provided with continuous fins not having any edge which causes a profile drag, instead of divided fins which utilizes edge effect for disturbing the flow of the primary fluid for improved heat transmission, and hence the pressure loss of the flow of the primary fluid is reduced remarkably.
In Japanese Patent Application No. 59-264087, only the performance of the heat exchanger, such as improvement in heat transmitting performance and reduction in pressure loss, is stated, however, nothing is mentioned regarding measures of manufacturing the heat exchanger, such as the manner of arranging the fins in layers and the manner of joining the pipes to the fins. Furthermore, since the pipes for passing a secondary fluid therethrough have a circular cross section, the overall sectional area of the fluid passages is reduced.